Replacing car brake pipes by micrabits

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No one in the trade likes changing brake pipes. You have to work in the dirtiest rustiest crevices of the car. Clips break, pipe ends round, seize and strip. Brake fluid leaks down your sleeve and all the time you are hoping the bleed screws slacken and the master cylinder seals do not flip.
So based on my years in the trade being landed with this job, here are my hints and tips on how to make the job easier and avoid crying in front of your mates!

1. Preparation. Soak every brake pipe end and bleed screw you are likely to need to remove with WD40 or similar. Give the loose Juice a good 15 minutes to soak in. For stubborn ends or bleed screws, slowly pour boiling water over them. Heating them with a gas burner risks melting seals in wheel cylinders or callipers and plastic clips but boiling water, poured slowly usually does the trick.


2. Cut the rot out! Do not bugg*r about with brake pipe spanners trying to take old brake pipes off. Cut the pipe with a decent pair of side cutters and get a tight fitting socket onto the end. You are going to be replacing the pipe anyway so why preserve it?  If you are removing a pipe that you will need to refit then use a brake pipe/flare nut spanner. Most cars have metric fittings nowadays but if you end up having to do this job a lot it might be worth kitting yourself out with a set of AF spanners too. As they are all slightly larger/smaller than the metric ones it comes in handy if you are removing stubborn or heavily corroded brake pipe ends

3. Insulating tape. If you are fitting a new brake pipe over the top of a petrol tank or along the engine bulkhead behind everything there is nothing more annoying than getting the pipe in position only to find the end has slid back down the pipe! Sticking a bit of insulating tape or similar is enough to hold the end at the end it should be. If you have to thread the pipe into an awkward place or behind loads of stuff take some single core wire to the old pipe and pull it through. When you have to fit the new pipe tape the wire to it, pull it back through and it will position the pipe as it should be. Easy!

4. Shaping. I have watched people shape the new brake pipe then try to fit it. Why? With the exception of tight radius bends you do not heed to do this as you end up bending the thing about as you fit it. Uniform bends can be made by bending the pipe round a socket etc. I have never seen the need to buy one of those pipe bender things!

5. Secure mounting. Most replacement brake pipes are made of copper or Nickel and copper. Copper hardens with movement so make sure your brake pipes are securely mounted or they will break. Make sure they will not rub against anything as copper is quite soft and wears fast. If you cannot avoid it slide some windscreen washer pipe over it to stop it wearing. If you break the small plastic mounting clips (which always seems to happen to be!) replace them by cable tying it to something substantial. Never mount brake pipes on exhausts, steering components or brake pedal rods. It sounds obvious but having been an Mot tester for a few years now you are often shocked with some of the places people have mounted replacement pipes!

6. Brake pipes and the M.O.T. Contrary to what certain fast fit centres and car dealers will tell you, surface rust on a brake pipe is not necessarily a failure! As it states in the MOT manual (3.6 Page 1) ‘Reason for rejection c. A brake pipe excessively chafed, corroded or damaged. Note: Chafing corrosion of or damage to a rigid brake pipe so that its wall thickness is reduced by 1/3 (eg approximately 0.25mm for a typical hydraulic brake pipe) is a reason for rejection. Put simply if the brake pipe is visibly thinner or pitted to the extent it may burst open whilst driving will fail.
Surface corrosion, slight chafing or flaking paint on first impressions may look bad but the tester is allowed to remove loose rust or paint with the ‘corrosion assessment tool spade end’ and at his discression decide whether the pipe has rotted to the extent that it may burst.
Other ways your rigid brake pipes can fail the MOT are if the pipe or ends are leaking (obviously!) if the pipe is inadequately supported or mounted (hanging off) or inadequately repaired (like cutting a burst bit of rigid pipe out and putting a but of rubber hose in instead. Seen that too!)
You can however cut the corroded part off a rigid brake pipe, flare the end and make a small pipe up to replace the corroded bit as long as proper brake pipe ends and pipe are used and it does not leak etc.

There, that should keep the language cleaner next time you have to do this.
See my other guides for hints and tips on how to bleed it all when you are done!
Good luck!

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